1. Field of the Invention
This invention relates to phosphate processes and more particularly to the production of high grade phosphate products from phosphate tailings and debris waste material and the production of a sand product for land reclamation or for use in glass, cement and the like.
2. Description of the Prior Art
Various types of methods have been devised by the prior art for processing raw phosphate ore into phosphate by-products including phosphoric acid, superphosphoric acid, feritilizers and the like. The various processes have been adapted in accordance with the type of phosphate ore present in various parts of the world and in accordance with the amount of phosphate contained in the ore matrix. Different grade matrix ores required different processes for extracting the phosphate from the ore in the most economical way.
The double float process is commercially used for the beneficiation of phosphate ore when the phosphate ore matrix contains impurities such as silicate materials. In this process the beneficiation of phosphate ore begins by digging the ore matrix from the ground. The ore matrix is used to form a slurry with water and is then pumped to a beneficiation plant. The coarse phosphate rock is screened out on a screen size generally ranging from +14 to +20 mesh. Material passing through the screen is the +20 mesh deslimed at 150 mesh. The material passing 150 mesh is called "slimes" and contains mostly clay, silica and phosphate. The slime is typically discarded in the conventional double float process. The usable ore typicaly -20 to +150 mesh is passed through a first flotation process for extracting the phosphate from the deslimed matrix. The usable ore is treated with a fatty acid fuel-oil (an anionic agent) conditioned in an alkali solution which causes the desired phosphate ore to float upon an underfloat. The underfloat, generally called "rougher tailings" is discarded in the conventional float process. The desired phosphate ore or overfloat, typically called "rougher concentrate" is deoiled with sulphuric acid to remove the anionic reagent and is then washed with water. Thereafter the washed overfloat is treated with an amine and kerosene (cationic reagent) in a second flotation process. The second flotation process removes silica whch floated during the first flotation process to produce a final concentrate grade of 70-76 percent BPL (bonded phosphate of lime) which is the desired product from the flotation process. The froth product tailings which are separated in the second flotation process from the final concentrate grade of phosphate is discarded under most prior art flotation processes. This froth product tailing contains from 8-25 percent BPL, but have been considered waste and discarded since there has not been an efficient and inexpensive method of extracting the 8-25 percent BPL from the froth product tailing.
Arthur Crago disclosed in U.S. Pat. No. 2,293,640 a method of concentrating phosphate materials from ore which comprises, in the first step, subjecting the ore to an aqueous pulp to a concentrating operation with negative ion reagents to separate a rougher concentrate of the phosphate values admixed with entrained silicious gangue. The second step of the Crago process involved treating the rougher phosphate concentrate with a mineral acid to remove the effect on both the phosphate and the silica particles of the negative ion reagent used in the production of the rougher concentrate. The third step of the Crago process included subjecting the acid-treated rougher concentrate in an aqueous pulp to a concentrating operation with a positive ion reagent which is a selective collector for the gangue in the rougher phosphate concentrate to separate out the material largely composed of silicious gangue thereby producing the final phosphate concentrate.
A further improvement of the Cargo process was disclosed by James D. Duke et al in U.S. Pat. No. 2,753,996. Duke et al improved upon the Crago method since Duke recognized the loss of phosphate in the silicious froth product since in practice it is impossible to produce a pure silica float. In the concentration of phosphate material by flotation employing only negative ion reagents, the middling product from the cleansing operation is often returned and passed through the system again with a new feed. However, the silicious froth product cannot be treated as a middling in that way. In attempting to following such a procedure in practicing the Crago method, a considerable amount of silica floats with the rougher concentrate thus lowering the grade of the finished phosphate concentrate. In addition, some of the phosphate does not float, thus causing a loss of phosphate in the tailings and the accumulation of phosphate in the middling which is returned to the original feed. In the practice of the Crago method, the silicious froth product containing a large amount of the silica removed from the rougher flotation product was discarded and a considerable amount of phosphate must be discarded.
The rougher tailings and froth product is usually stored in large waste areas since it is considered too low grade to economically reclaim the phosphate. In addition, this material is radioactive which prohibits the use of this material for filling the large phosphate quarries. Many acres of land cannot be economically reclamated due to the radioactive waste piles and the phosphate quarries.
Therefore, it is an object of this invention is to provide a method of beneficating phosphate tailings and debris waste material to produce a sand suitable for use in glass, cement or the like.
Another object of this invention is to provide a method of beneficating phosphate tailings and debris waste material to reclaim heavy minerals contained in the waste debris.
Another object of this invention is to provide a method of beneficating phosphate tailings and debris waste material to produce sand and heavy minerals with satisfactory radiation levels to enable land reclamation by filling phosphate quarries with radiation reduced waste products.
The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description describing the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.